Looks interesting and like it would be used at all events as standard.
Our club has used the Pete Dutton version to check our targets when we do a Winter League shoot in our region. Since then we have only had 3 whistles of which none were for target operation but strings getting caught up.
It gives us confidence on the targets, however even if the targets work it can highlight any that are temperamental. The sparrow targets are the ones that seem to gave most issues to us.